US officials condemned CNN as "disgusting" after the television network secretly reported entries from a diary kept by the US ambassador to Libya and discovered after his death.

CNN last week reported that Ambassador Christopher Stevens feared he was on an al-Qaeda "hit-list" before he was killed in an attack on the American consulate in Benghazi earlier this month.

They added that he was concerned about a "rise in Islamic extremism" in the city. Viewers were told that the information was obtained from a "source familiar with Ambassador Stevens's thinking".

This was in fact a journal of handwritten entries by Mr Stevens, which was found by a reporter on the floor of the compound where the diplomat was fatally wounded.

After being informed of the discovery, Mr Stevens's family repeatedly told CNN that they wanted to inspect the book before giving them permission for its contents to be reported.

However, after eventually agreeing to hand over the seven-page hard-back book through a third party, the network disclosed Mr Stevens's fears about al-Qaeda and security threats before the family's permission was granted.

It only informed viewers of the original source after being questioned by a media reporter for the Huffington Post, a news website, who had been tipped off about the journal's existence.

"Some of that information was found in a personal journal of Ambassador Stevens in his handwriting," Anderson Cooper told viewers on Friday. "We came upon the journal through our reporting and notified the family. At their request, we returned that journal to them. We reported what we found newsworthy in the ambassador's writings." The network was condemned as "disgusting" and "indefensible" for going against the family's wishes by Phillippe Reines, a senior aide to Hillary Clinton, the US Secretary of State.

He asked in a statement: "Whose first instinct is to remove from a crime scene the diary of a man killed along with three other Americans serving our country, read it, transcribe it, email it around your newsroom for others to read, and only when their curiosity is fully satisfied thinks to call the family or notify the authorities?"

A spokesman for the network said it had pursued details gleaned from the journal with its own reporting before broadcasting them. He accused the State Department of "attacking the messenger".

"CNN did not initially report on the existence of a journal out of respect for the family," the spokesman said. "But we felt there were issues raised in the journal which required full reporting, which we did."